Cleaning apparatus for electrostatic copy devices

ABSTRACT

Cleaning apparatus for cleaning the residual toner image from an electrostatic plate of an electrostatic reproduction apparatus incorporates an open celled foam wiper which is mounted for wiping engagement with the plate. The foam wiper is mounted adjacent a conductor which is biased to attract charged toner particles to the wiper as the toner image moves relative therepast. The wiper is periodically cleaned by a serrated or grooved portion of the plate which follows the image and mechanically dislodges toner from the wiper. A reverse bias is applied to the conductor as the serrations on the plate move past the wiper creating a field between the wiper and the plate which repels toner from the wiper to the plate. The toner is carried by the serrations on the plate to the developer unit for use by the electrostatic reproduction apparatus.

United" States Patent 5 1391 Harbour, Jr. et al.

CLEANING APPARATUS FOR ELECTROSTATIC COPY DEVICES Inventors: Wilmer P. Harbour, Jr.; Carl A.

Queener, both of Lexington, Ky.

Appl. No.: 210,889

us. c1. .355/15, 15/15, 15/25651 Int. Cl. ..G0'3 15/22 Field of Search ..3s5/15; 15/15, 256.51,

References Cited UNITED STATES PATENTS Tanaka et al. ..355/l5 X Fisher et al ..355/l5 Royka et al. ..355/l5 Primary Examiner-Samuel S. Matthews Assistant Examiner-Fred L. Braun Attorney-John W. Girvin, Jr. et al.

[57] ABSTRACT Cleaning apparatus for cleaning the residual toner image from an electrostatic plate of an electrostatic reproduction apparatus incorporates an open celled foam wiper which is mounted for wiping engagement with the plate. The foam wiper is mounted adjacent a conductor which is biased to attract charged toner particles to the wiper as the toner image moves relative therepast. The wiper is periodically cleaned by a serrated or grooved portion of the plate which follows the image and mechanically dislodges toner from the wiper. A reverse bias is applied to the conductor as the serrations on the plate move past the wiper creating a field between the wiper and the plate which repels toner from the wiper to the plate. The toner is carried by the serrations on the plate to the developer unit for use by the electrostatic reproduction apparatus.

9 Claims, 3 Drawing Figures CLEANING APPARATUS FOR ELECTROSTATIC I COPY DEVICES CROSS REFERENCES TO RELATED APPLICATIONS A Electrophotographic Development Apparatus, Al-

lison I-I. Caudill, inventor, filed Dec. 17, I971.

BRIEF BACKGROUND OF INVENTION 1. Field This invention relates to the cleaning of toned electrostatic images on a plate and, more particularly, to an improved foam wiper cleaning apparatus.

2. Description of the Prior Art In well-known electrostatic printing processes, an electrostatic plate bearing a latent electrostatic image is developed by applying a developer material including charged electroscopic toner particles to the plate. The charged toner is selectively attracted to the image areas on the plate and iselectrostatically maintained thereon. The toned image is thereafter transferred to a support surface suchas paper and thereafter permanently affixed to the support surface. Transfer of the toner particles from-the image area on the plate to the support surface isoften effected by a corona generating device which imparts an electrostatic charge to attract the toner particles from the plate to the support surface. Other transfer techniques such as pressure transfer and heat transfer are also utilized. In any event, a residual toner image usually remains on the plate after transfer which must be cleaned therefrom before the plate may be reused for subsequent imaging.

Well-known brush and web-type cleaning apparatus have often-been employed to remove the residual toned image from the electrostatic plate in prior electrostatic printing apparatus. The brush-type cleaning devices usuallycomprise one or more rotating brushes which brush the toner powder from the plate into a stream of air which is exhausted through a filtering system. Often, a knockoff bar orsimilar apparatus is utilized in conjunction with the rotating brush to free the toner particles from the brush thus maintaining the brush operable over a number of cycles. It has further been sug gested to utilize a belt form of brush which passes over a mandrel having an electrical field applied thereto which tends to repel toner from the brush as the brush passes thereover at a position remote from the plate.

The web cleaning devices effect removal of the residual toner by passing a web of fibrous material over the plate surface. The web is thereafter cleaned at a remote point so that it may again be reused or is disposed of as a consummable item.

While the brush and web cleaning apparatus of the prior devices satisfactorily clean the electrostatic plate for a limitednumber of operations, they are generally complex and occupy a great deal of space in the electrostatic printing apparatus, thereby preventing such machines from being compact. Further, most such systems permanently remove the residual toner from the electrostatic printing apparatus so that the toner cannot be reused without necessitating a messy transfer operation by the operator. Both the brush-type cleaner and the web-type cleaner must be frequently replaced due to wear and accumulation of toner particles on the individual brush and web fibers. In addition, an elaborate and noisy vacuum and filtering system is necessary to collect the residual toner particles removed from the electrostatic plate.

A further prior art approach has suggested the utilization of a rubber wiper blade which scrapes the residual toner particles from the electrostatic plate. In one suggested embodiment, the plate is in the form of a drum having axial grooves following the image area i which receive the accumulated toner particles as the grooves rotate under the rubber wiper. The grooves then transport the toner particles to the developer unit. It has been found that such rubber wipers catastrophically fail to remove toner particles from thesurface of the plate after a relatively few number of operations.

A further prior art approach has suggested the utilization of a cleaning roller made of a resilient or elastic material such as natural or synthetic rubber or sponge which is mechanically biased in compressed rolling contact against the electrostatic plate. The rubber roller is continuously cleaned by a brush which dislodges toner particles therefrom at a position that is not adjacent the plate. While such a roller provides excellent cleaning characteristics'over a relatively few number of reproduction cycles, it soon becomes clogged with toner particles'and is no longer effective in removing tonerfrom the plate.

SUMMARY In order-to overcome the above-noted shortcomings of the prior art and to provide a compact cleaning apparatus which consistently cleans large quantities of residual toner from an electrostatic plate over numerous reproduction cycles without becoming appreciably worn or clogged with toner, a porous trostatic plate travelsin a closed loop and contains serrations thereon following the image area which mechanically dislodge the toner particles from an open-celled foam wiper as they travel therepast. An electrical field is simultaneously applied causing the toner particles to move toward the serrated portion of the electrostatic plate. The toner particles are then transported by the serrated portion of the plate to the developer unit for reuse by the electrostatic reproduction apparatus. The cleaning operation of the foam wiper is further enhanced by applying an electrical field thereto which attracts toner from the image area of the plate, this field being opposite that which is utilized when purging the toner from the cleaning member.

Accordingly, it is the principle object of the invention to provide an improved reusable electrostatic plate cleaning system.

It is a further object of this invention to provide a cleaning system adapted to reduce toner consumption.

A still further-object of this invention is to provide a compact cleaning system for use in an electrostatic reproduction machine.

The foregoing objects, features, and advantages of the invention will be apparent from the following more particular description of the preferred embodiment of the invention as illustrated in the accompanying drawings. I i

In the drawings; a

FIG. 1 is a schematic illustration of a conventional electrostatic reproduction apparatus incorporating the cleaning apparatus of the present invention.

F IG. 2 is an enlarged schematic diagram of the surface of the serrations and foam wiper of the cleaning apparatus of the present invention.

FIG. 3 is a schematic pictorial illustration of the mountingmeansfor the foam wiper of the cleaning ap paratus of the present invention.v

DESCRIPTION Referring now to the drawings, and more particularly to FIG. 1 thereof, a schematic illustration of a conventional electrostatic reproduction apparatus incorporating a cleaning apparatus of the present invention as depicted. v

' The reproduction apparatus comprises'a plurality of processing stations located about a cylindrically shaped electrostatic photosensitive plate 11. The cylindrical plate comprises a layer of photoconductive material Ila superimposed over a conductive nonmagnetic backing layer 12. A suitable photoconductive material is disclosed in US. Pat. No. 3,484,237 issued Dec. 16, 1969.]The backing layer can comprise a substrate made of an insulating materialsprayed with aluminum, the aluminum providing a requisite conduction path to ground. The photoconductive material is sensitized by a corona generating device 13 as the plate rotates therepast in the direction of arrow 15. A light image of the copy 17 to be reproduced is projected onto the sensitized surface of the electrostatic photosensitive plate 11 rotating thereunder to form an electrostatic latent image thereon. The rotating plate thereafter passes a magnetic brush developing station 19 where multicomponent developer material including electrostatically charged toner is applied to the surface of the electrostatic photosensitive plate 11 containing the electrostatic image thereon. The charged toner particlesare preferentially attracted to the latent image on the plate 11 and are subsequently transferred to a support surface 21 as the plate rotates therepast by conventional electrostatic transfer. The plate continues to rotate past a precleaning corona 25 which charges the residual toner particles on the surface of the plate. Thereafter, the plate rotates past the cleaning station 27 which removes the residual toner from the surface of the plate prior to the arrival of the plate at the corona generating device 13. I

The trailing edge 29 of the image area on the electrostatic photosensitive plate 11 is followed by a plurality of serrations or grooves 31 on the surface of the plate 11, the serrations being oriented in an axial direction with respect to the cylindrical surface. The serrations are formed from a metallic block 32 which is grounded and contains no photoconductive material thereover. The serrations are wipingly engaged by the apparatus at the cleaning station 27 as will be described and which is applied to the plate 11 as it rotates therepast- The principle components of the developer material are electroscopic toner and a ferromagnetic carrier material. Suitable materials for use as toners are well known in the art and generally comprise finely divided resinous material capable of being attracted and held by electrical charges. Examples of toners which can be 2 employed are commercially marketed by the International Business Machines Corporation as IBM part no.

1162057 and IBM part no.1 162051. The IBM part no.

I 162057 toner comprises-a copolymer of styrene/n-butylmethac'rylate resin, maleic anahydride modified polyester, polyvinyl stearate plasticizer, and carbon black pigment. The IBM part'no. 1162051 toner cornprises a copolymer of n-butymethacrylate/methymethacrylate resin, maleic anahydride modified polyester, polyvinylbutyral plasticizer, carbon black pigment, and a fumed silica physically mixed in the toner after compounding. Many well-known suitable ferromagnetic carrier materials can be utilized,

the carrier particles generally being between 50 and 1,000 microns in size. Often, the carrier'particles are manufactured by coating a ferromagneticcore or head with a material which triboelectrically interacts with the selected toner to produce a desired charge on the toner in order to provide good imaging quality. An example of such a carrier and the method by which it can be made to obtain a desired triboelectric characteristic for any selected toner is disclosed in the aforereferenced copending application of. William J. Kukla,etal. g 1

The developing station 19 further incorporates a bucket conveyor 35' which delivers the developer material 33 to the surface-of a cylindrical magnetic brush unit 37. The magnetic brush unit 37 magnetically attracts the ferromagnetic carrier thereto, the toner being electrostatically held by the carrier. The developer material thus attracted to the surface of the magnetic brush unit 37 is rotated with the brush unit in the direction of arrow 39 into contact with the electrogrooves as the drum continues its rotation within the developer station 19. The detailed operation of the developer unit at the developer station 19 is described in the aforereferenced copending application of Allison v H. Caudill, et al.

As has been described, the toned image leaving the developer station 19 is transferred to a support sub-.

strate 21. -A' corona generating device 41 creates an electrostatic charge on the support substrate causing the toner to be preferentially attracted thereto from the surface of the electrostatic photosensitive plate 11. While the major portion of the toned image is transferred to the support substrate 21, a residual image remains which must be cleaned from the electrostatic photosensitive plate 11 prior to a subsequent imaging cycle. Accordingly, the residual toner image is rotated past a preclean'corona 25 which enhances the charge on the toner particles. Assuming that the toner particles are triboelectrically charged in the developer unit positively with respect to the image on the photoconductor,. preclean corona 25 would be a positive preclean corona and transfer corona 41 would be a negative corona.

The residual toned image thereafter passes cleaning station 27. The cleaning station 27 comprises an opencelled foam wiper 50 mounted for wiping engagement with the surface of the electrostatic photosensitive plate 1 1. It has been found that a cleaning wiper of two inches of effective lengthreadily cleans an image area of 14 inches in length. When utilizing the aforereferenced IBM part no. 1162051 toner, the open-celled foam wiper may be made of polyurethane foam. Various other porous or se miporous compliant elastomeric materials such as neoprene foam, polytetrafluoethylene felt or sponge rubber may be utilized. It is important that the interstitial voids in the selected material be of a size great enough to entrain a plurality of toner particles.

Thewiper 50 is mounted on a plastic holder 51 which is, in turn, mounted on a conductive backing plate 53. The conductive backing plate 53 is connected to a high voltage power supply 55 through a high voltage switch 57. The high voltage power supply 55 applies a potential of approximately 8 KV to the backing plate when the residual toned image passes the cleaning member causing the positively charged toner particles to be attracted toward the foam wiper because of the field created between the conductive backing plate 53 and the grounded conductive backing layer 12 of the electrostatic photosensitive plate 11. When the serrations 31 rotate past the foam wiper, the circuit breaker or sensing means 59 mechanically keyed to the rotation of the cylindrical electrostatic photosensitive plate 11 senses that the serrations 31 are adjacent the foam wiper and thereby causes the high voltage switch 57 to transfer thusly connecting the conductive backing plate 53 to the highvoltage power supply 61. The power supply 61 provides an output potential of approximately +8 KV which thus creates an electrical field between the conductive backing member 53 and the grounded block 32. The field is oriented to repel the positively charged toner particles from the wiper 50 toward the serrations 31 and is applied when the serrations 31 reach the position depicted in FIG. '1. It has been found that conductive porous or semiporous elastomeric materials such as conductive neoprene may be utilized as the wiper thereby allowing equivalent fields to those obtained with the insulating wiper materials at bias voltages of lower magnitude.

The. serrations mechanically engage the foam wiper 50 as they rotate therepast causing toner particles to be dislodged therefrom. The thusly dislodged charged toner particles are moved within the electrical field to the serrations and are transported by the serrations 31 to the developer station 19. The high voltage switch 57 again transfers as the image area nears adjacency with the wiper 50.

Referring now to FIG. 2 of the drawings, an enlarged schematic diagram of the surface of the serrations and the foam wiper is depicted. The foam wiper 50presents a plurality of open cells 71 which fill with toner particles as the wiper engages the electrostatic plate. When the serrations 73 located on the grounded block 32 pass the open cells of the foam wiper 50, the toner particles are loosened by the flipping movement of the cell walls on release from the serration ridge 75. The thusly loosened positively charged toner particles are driven into the serration groove 77 by the electrical field where they remain until they reach the developer station 19 ofFIG. 1.

Referring now to FIG. 3 of the drawings, a schematic pictorial illustration of the mounting means for the foam wiper of the cleaning apparatus of the present invention is depicted. The foam wiper 50 is mounted for pressure contact with the surface of the plate 11 of FIG. 1. The mounting means includes a toggling means which is operative to move the wiper 50 away from the surface of the plate 11 whenever it is desirous to change the wiper. In order to move the wiper 50 away from the surface of the plate 1 1, the crank 81 is rotated in a counterclockwise direction about pivot 83 causing the wiper 50 and its associated mounting means to pivot about pivot 85 in a clockwise direction. The operator may thereafter engage the tab 87 pulling the plastic mounting means 51 and the foam wiper 50 attached thereto from the conductive backing plate 53 of FIG. 1.

While the above description has related to a porous complient wiper which is fixedly mounted with respect to a rotating cylindrical plate, it is recognized by those skilled in the art that the wiper could take the form of a cylindrically shaped member adapted to rotate about an axis parallel to the axis of the drum. The wiper thus constructed would mounted over a conductive core which would be biased to attract toner particles from the plate into the wiper and biased to repel toner particles from the wiper into the grooves or serrations. It is further recognized that such a device could incorporate a second plate having the serrations thereon for wiping engagement with the portion of the wiper which is not engaging the electrostatic plate. It is further recognized by those skilled in the art that a noncylindrical electrostatic plate could be utilized. For example, a belt-type electrostatic plate well known in the art could be constructed having serrations or grooves located therein at nonimage areas and directed transverse to the direction of belt movement at the cleaning station. It has further been found that effective cleaning of the plate is accomplished by utilizing a bias on the cleaning member only when the serrations are adjacent thereto.

Further, as is appreciated by those skilled in the art, various forms of mechanical purging elements can be utilized such as knurled surfaces, flame sprayed surfaces, or other roughened surfaces, it being important that the mechanical element provide a dislodging force to the toner in the porous wiper at the time that the field is applied.

While the invention has been particularly shown and describedfwith reference to a preferred embodiment thereof, it should be understood by those skilled in the art that the foregoing and other changes in form and detail may be'made therein without departing from the spirit and scope of the invention.

What is claimed is:

'1. Cleaning apparatus for removing electrostatically charged ftoner particles from a surface of an electrostatic platecomprising: v

a rigid member having a roughened surface;

a porous compliant wiper having an outer surface containing a plurality of pores having cell walls mountedforwiping engagement with the surface of the plate for removing charged toner particles therefrom and for entraining a plurality of removed charged toner particles in said plurality of pores and mounted for wiping engagement with the -surfaces of said rigid member, said plate and saidwiper whereby at least a portion of the outer 'surfaceof said wiper is alternately engaged by the surface of the plate'and said surface of the rigid member, said moving engagement between the surfaces of said rigid member and said wiper moving the cell walls of said plurality of pores to dislodge charged toner entrained therein;

' electrical bias means for applying an electrical field between said rigid member and said wiper of a I polarity to repel charged toner from said wiper to said'rigid member when the outer surface of the wiper engages said surface of the rigid member. 2. The cleaning apparatus set forth in claim 1 further comprising:

second electrical biasmeans'for applying an electrical field between said plate and said wiper of a polarity to attract charged toner from the surface of' the plate to said wiper when said wiper engages the surface of the plate. 3. The cleaning apparatus set forth in claim 1 further comprising:

conductive mounting means for mounting said wiper in'wipirig engagement with the surface of the plate, said bi'as means applying a bias to said mounting means thereby creating said electrical field. 4. The vcleaning apparatus set forth in claim 1 wherein the surface of the plate and the rigid member are serially mounted for closed loop motion with respect to said wiper, said wiper sequentially alternately engaging the surface of the plate and said rigid member. v

5. The cleaning apparatus set forth in claim 4 further comprising: 7

second electrical bias means for applying an electrical field between said plate and said wiper of a polarityto attract charged toner from the surface of the plate to said wiper when said wiper engages the surface of the plate.

6. The cleaning apparatus set forth in claim 4 further comprising: 7 I

conductive mounting means for mounting said wiper in wiping engagement with the surface of the plate,

said bias means applying a bias to said mounting means thereby creating said electrical field. 7. An electrostatic reproduction apparatus comprisa member mounted for closed loop motion in a first direction having an electrostatic imaging surface and at least one groove extending transverse to said first direction; Y drive means for driving said member in said first direction in a closed loop past a plurality of processing stations; an imaging station for creating a latent electrostatic image on said imaging surface;

a developer station for applying charged toner to said imaging surface; a transfer station for transferring the major quantity of said toner to a substrate;

a cleaning station for cleaning residual toner from said imaging surface, said cleaning station comp g;

a porous compliant wiper mounted for wiping engagement with said member for removing charged toner therefrom; a

sensing means for sensing the relative position of said at least one groove and said wiper,

bias means, responsive to said sensing means for applying an electrical field between said member and said wiper of a polarity to repel charged toner from said wiper to said at least one groove of said member when said wiper engages said groove whereby toner is transported from said wiper to said developer station by said at least one groove.

8. The electrostatic reproduction apparatus set forth in claim 7 further comprising: second bias means for applying an electrical field between said imaging surface and said wiper of a polarity to attract charged toner to said wiper from said imaging surface; v switch means responsive to said sensing means for alternately actuating said first mentioned bias means and said second bias means, said first mentioned bias means being actuated when said at least one groove engages saidwiper, said second bias means forth 

1. Cleaning apparatus for removing electrostatically charged toner particles from a surface of an electrostatic plate comprising: a rigid member having a roughened surface; a porous compliant wiper having an outer surface containing a plurality of pores having cell walls mounted for wiping engagement with the surface of the plate for removing charged toner particles therefrom and for entraining a plurality of removed charged toner particles in said plurality of pores and mounted for wiping engagement with the surface of the rigid member; drive means for effecting relative movement between the surfaces of said rigid member, said plate and said wiper whereby at least a portion of the outer surface of said wiper is alternately engaged by the surface of the plate and said surface of the rigid member, said moving engagement between the surfaces of said rigid member and said wiper moving the cell walls of said plurality of pores to dislodge charged toner entrained therein; electrical bias means for applying an electrical field between said rigid member and said wiper of a polarity to repel charged toner from said wiper to said rigid member when the outer surface of the wiper engages said surface of the rigid member.
 2. The cleaning apparatus set forth in claim 1 further comprising: second electrical bias means for applying an electrical field between said plate and said wiper of a polarity to attract charged toner from the surface of the plate to said wiper when said wiper engages the surface of the plate.
 3. The cleaning apparatus set forth in claim 1 further comprising: conductive mounting means for mounting said wiper in wiping engagement with the surface of the plate, said bias means applying a bias to said mounting means thereby creating said electrical field.
 4. The cleaning apparatus set forth in claim 1 wherein the surface of the plate and the rigid member are serially mounted for closed loop motion with respect to said wiper, said wiper sequentially alternately engaging the surface of the plate and said rigid memBer.
 5. The cleaning apparatus set forth in claim 4 further comprising: second electrical bias means for applying an electrical field between said plate and said wiper of a polarity to attract charged toner from the surface of the plate to said wiper when said wiper engages the surface of the plate.
 6. The cleaning apparatus set forth in claim 4 further comprising: conductive mounting means for mounting said wiper in wiping engagement with the surface of the plate, said bias means applying a bias to said mounting means thereby creating said electrical field.
 7. An electrostatic reproduction apparatus comprising: a member mounted for closed loop motion in a first direction having an electrostatic imaging surface and at least one groove extending transverse to said first direction; drive means for driving said member in said first direction in a closed loop past a plurality of processing stations; an imaging station for creating a latent electrostatic image on said imaging surface; a developer station for applying charged toner to said imaging surface; a transfer station for transferring the major quantity of said toner to a substrate; a cleaning station for cleaning residual toner from said imaging surface, said cleaning station comprising; a porous compliant wiper mounted for wiping engagement with said member for removing charged toner therefrom, sensing means for sensing the relative position of said at least one groove and said wiper, bias means, responsive to said sensing means for applying an electrical field between said member and said wiper of a polarity to repel charged toner from said wiper to said at least one groove of said member when said wiper engages said groove whereby toner is transported from said wiper to said developer station by said at least one groove.
 8. The electrostatic reproduction apparatus set forth in claim 7 further comprising: second bias means for applying an electrical field between said imaging surface and said wiper of a polarity to attract charged toner to said wiper from said imaging surface; switch means responsive to said sensing means for alternately actuating said first mentioned bias means and said second bias means, said first mentioned bias means being actuated when said at least one groove engages said wiper, said second bias means being actuated when said imaging surface engages said wiper.
 9. The electrostatic reproduction apparatus set forth in claim 8 further comprising: conductive mounting means for mounting said wiper in wiping engagement with said member, said switch means alternately connecting said conductive mounting means to said first mentioned bias means and to said second bias means. 